Standards
•Visual compression standards define the syntax of a bitstream i.e. how to decode a
compressed bitstream.
•It does not define how to create a bitstream
•For example the H.264 standard
Defines the codes used for different DCT values
The code that defines the start of an I, P, B frame
The order in which the bits are put together
The code that marks the start of motion information
and so on
•But it does not define HOW to do motion estimation, or HOW to generate a DCT coefficient
•Cleary it helps to have a bit of software which shows people how to all of these things and
that is called a REFERENCE DECODER there is usually also a REFERENCE ENCODER.
The standards bodies coordinate the creation and testing of these REFERENCE MODELS
for the standard. These are very important for engineers to have faith in the standards and
can build “Standards compliant” hardware or software modules.